Method for forming preformed material

ABSTRACT

A method for the shaping of a sheet of preform material. A flat planar (heated) sheet of preform material is held tightly between two elastomeric sheets, the sheets and preform material forming a laminate assembly. The laminate assembly is then formed about a mold having the desired contours. The elastomeric sheets maintain the preform material parallel to the surface contours of the mold as the molding process proceeds. A fluid such as air is flowed between the mold surface and the laminate assembly during the forming process to prevent the elastomeric sheets from binding on the mold surface. Wrinkles are eliminated in the final shape of the preform material, and fiber distortion of tears or rips in the material are minimized due to the fluid lubrication between the mold surface and the laminate assembly.

RELATED APPLICATION

This application is related to the application entitled "Apparatus forForming Preformed Material", Nazim S. Nathoo inventor, filed Apr. 17,1989, Ser. No. 338,683.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method of fabrication of preforms for theresin transfer molding process. A preform is the fiberglassreinforcement package that has the shape of the desired composite partand has the correct glass type (chopped or continuous) and glass fiberorientation (random or directed). The use of preforms in this processadvantageously reduces mold cycle times due to the more rapidpositioning of the preformed reinforcement material in the mold. Fewerparts are rejected because the actual distribution of the reinforcementin the mold may be checked before molding.

2. Discussion of the Prior Art

There are two basic approaches for fabricating preforms for the resintransfer molding process. In the first approach, fiberglassreinforcement is deposited directly on a screen. One example ofdeposition methods in this category is chopped glass spray-up, ordirected fiber placement. Such an approach may be studied in the articleentitled "Preforming for Liquid Composite Molding" by E. P. Carley et alpublished in Proceedings of the 44th Annual Conference of the Society ofthe Plastic Industry, Feb., 1989 session 10-B.

When chopped glass strands are sprayed to form a preform, consistentproduction results are difficult to achieve because of the inclusion ofa manual operation in the process. Local variations in fiber depositionup to 40% have been noted. Other difficulties in making preformssymmetrically balanced with regard to their vertical rotational axishave been encountered. Additionally, the minimum radius of curvaturewhich can be obtained using chopped strands and the air depositionprocess is relatively high due to the "springy" nature of the choppedstrands.

The second basic approach for fabricating preforms requires fabric asthe starting point for reinforcement, as noted in "Preforming ofUnifilo" by L. Pomini of Vetrotex St. Gobain, published in theReinforced Plastics Congress 13th, 1986 by the British PlasticsFederation Publication N293, London, England, and in "PreformingContinuous Filament Glass Mat" by Mark Hickling of Technical ServicesVetrotex U.K. Ltd., Wallingford, Oxon, (available NTIS). The fabric mayconsist primarily of random or continuous fibers.

Regardless of the type of fabric used, it is necessary to cut the fabricin a pattern that will cover the mold surface with the correct fiberorientation.

Once the fabric is cut, it has to be formed to the shape of the moldsurface. In hand-layup operations, the fabric is usually hand-fitted tothe surface in a relatively labor-intensive manner. Other methodsrequire that the fabric be tensioned in a machine frame while a set ofmatched-cavity dies form the fabric to the desired shape. (The design ofsuch a machine may be studied, for example, in the sales literature ofEMC Machinery, P.O. Box 9800, Fort Worth, Texas). This method generates20 to 25% waste of preform material due to the necessary trimming of theedge of the fabric to the edge of the mold. This wastage is due to theexcess material held by the frame beyond that required to reach theouter boundaries of the part. This method works best with randomcontinuous glass mat.

Use of the machine frame is limited either to forming the fabric to amold surface having simple contours, accepting a large number ofwrinkles in the final shaped preform, or rejecting a large number ofpreforms due to unacceptable fabric distortion or tearing.

In applications where tight control must be maintained on fabricthickness it is desirable to replace the chopped glass spray-up fiberdeposition which has thickness variations with fabric having uniformthickness. Additionally, undesirable channels are not formed throughfabric during the period that resin is flooded into the mold and throughthe fabric, because the fabric is not preferentially oriented as foundin sheet molding compounds. Consequently, mechanical properties andsurface finish are improved over sheet molding compound and sprayed-upfiber depositions by the use of fabric.

As the severity of the edge and contour topography within a moldincreases, the fabric tends to wrinkle when forced around the edges andcontours such that unwanted quantities of the fabric "bulge", fold over,wrinkle, and generally displace from a substantially planar positionadjacent the mold surface. Current technology therefore limits the useof preform fabrics to use within molds having gentle contours.

Superplastic aluminum diaphragms have been used to form metals and, morerecently, thermoplastic resin impregnated carbon fiber fabrics. Aluminumdiaphragms were required in the case of the thermoplastic impregnatedfabric because of the high temperature (approximately 700° F.) at whichthe thermoplastic resin softened to permit forming to occur. Thediaphragms can be used only once and, as a result, the process is quiteexpensive and does not lend itself to desired preform mass productionrequirements.

More recently, the superplastic aluminum diaphragms have been replacedwith a polymeric diaphragm, as noted in "Composites Update", Universityof Delaware, Autumn 1987. This diaphragm, like the superplastic aluminumdiaphragm, is not reusable.

A method needs be developed therefore that allows the use of fabricwithin a mold, wherein the mold has accentuated edge and contoursections. Such a method should lend itself to the mass production of thepreforms in an economical manner. The preform material during theforming process should not wrinkle nor tear, and preferably the fabricshould be "cut to fit", wherein expensive trimming of the fabric edgesis eliminated, after the preform material is shaped.

SUMMARY OF THE INVENTION

The method of the present invention of shaping a preform materialcomprises the steps of holding the preform material between twoelastomeric sheets to minimize wrinkles, tears, or folds in the preformmaterial during the shaping of the material, and thereafter molding thepreformed material to the preferred shape while the material is stillheld between the two elastomeric sheets. The preform material mayconsist of multiple layers (sheets).

Holding the preform material between the sheets ensures that thematerial does not wrinkle during the molding process, even when formedabout difficult edges and contours, since the material is held parallelto the mold surface by the sheets during the forming process. Theprocess therefore yields preforms of complex shapes not previouslyobtainable by prior art methods. The elastomeric sheets also spreadfabric forming stress concentrations away from "hard edges" on the moldsurface such that distortion of the fabric is held within acceptablelimits, so that the fabric does not tear during the forming process.Holding the material between the sheets prevents the material fromshifting during the forming process, such that the costly prior art edgetrimming operation is eliminated.

Use of the elastomeric sheets has an additional advantage. As the sheetswith the preform material held therebetween are formed about the moldsurface, lubrication is included between the sheets and the moldsurface, such that binding of the sheets on the "hard edges" of the moldis eliminated. Lubrication in the preferred embodiment is provided byflowing air between the sheets and the mold surface.

The sheets therefore "free float" over the hard edges on the moldsurface. The sheets, being impermeable to air, do not allow thelubricating air flow to blow through the fabric and thereby preventdistortion of any of the fabric's fibers during the air lubricationprocess.

The elastomeric sheets therefore minimize or eliminate any wrinkles inthe fabric since they maintain the fabric parallel to the mold surfaceduring the forming process, and by use of the air lubrication process,prevent binding of the sheets to the mold surface.

The apparatus of the present invention comprises two elastomeric sheetswhich hold the preform material therebetween, (the sheets and preformmaterial forming what is described hereinafter as a laminate assembly).The apparatus also includes a mold having the desired contour, means forforming the laminate assembly about the mold contours, as well as meansfor lubricating the surface of the laminate assembly and the surface ofthe mold as the laminate assembly is formed about the mold.

A vacuum is developed between the two elastomeric sheets to hold thepreform material therebetween during portions of the molding process.The sheets are reusable. After each preform is molded and removed frombetween the sheets, new unformed preform material is placed between thesheets and the forming process repeated.

It is therefore an object of the present invention to eliminate theexpensive edge trimming operation after each preform has been shaped bythe method of the present invention.

It is a feature of the present invention to hold the preform materialbetween two elastomeric sheets, to minimize wrinkles in the preformmaterial and dissipate stress concentrations in the preform material andthereby eliminate or minimize tears in the fabric.

It is a feature of the present invention to flow fluid lubricationbetween the mold surface and the laminate assembly to prevent and/orminimize binding of the laminate assembly on the mold surface.

These and other features, objects and advantages of the presentinvention will become apparent from the following detailed descriptionwherein reference is made to the figures in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation in cross-section of the preformmaterial shaping apparatus, including the upper mold, lower mold, upperand lower sheet frame, upper and lower elastomeric sheets, and preformmaterial.

FIG. 2 shows a schematic representation in cross-section of the laminateassembly, comprised of the upper and lower elastomeric sheet and thepreform material held therebetween, positioned above the surface of thelower mold.

FIG. 3 shows a schematic representation in cross-section of the uppermold about to engage the top of the laminate assembly.

FIG. 4 shows a schematic representation in cross-section showing theupper mold engaging the laminate assembly.

FIG. 5 shows a schematic representation in cross-section showing theupper and lower molds tightly compressed about the laminate assembly.

FIG. 6 shows a schematic representation in cross-section of the shapedpreform supported by the lower elastomeric sheet.

FIG. 7 shows a detail of a portion of FIG. 4, in particular the air flowthrough the fluid lubrication openings and past the laminate assemblysurface.

FIG. 8 shows a schematic representation of a shaped preform formed byuse of a female mold having accentuated contours.

FIG. 9 shows a schematic representation in cross-section of aconcentration of fluid lubrication openings in a typical mold structure.

FIG. 10 shows a detail of a portion of FIG. 3, in particular the sealsused between the lower mold, and upper and lower sheet frames.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1 a preform material shaping apparatus 10 usefulfor shaping preform material 12 is shown. The preform material maycomprise continuous strand mat, chopped strand mat, biax and triaxfabric, woven roving, or for example a combination of woven roving onone side with chopped strand mat on the other side. It should be wellunderstood that other preform materials may be used in accordance withthe teachings of the present invention.

The preform material in the preferred embodiment is coated with a sizingused to dimensionally stabilize the material, typically after the sizing(and the preform material) has been heated, formed and thereafterallowed to cool in the desired finished shape. It should be wellunderstood that other preform materials may be used that do not have asizing material applied to them, if the materials are still capable ofretaining the desired contours after removal from a mold.

The apparatus can be seen to include a lower mold 14 having a lower moldsurface 16 of the desired shape. The lower mold surface 16 includes atleast one first fluid lubrication opening 18 defined therethrough andplaced in fluid communication with first fluid lubrication means 20(FIG. 2) such as a fluid lubrication pump 22, the fluid used forlubrication in the preferred embodiment being air. It should be wellrecognized that other mediums may be used to effectively lubricate andallow sliding of the surfaces of the laminate assembly relative to therespective mold surfaces, though it is recommended that dry substancessuch as powders be used if a gaseous substance such as air is notavailable.

The lower mold surface 16 can also be seen to include at least onevacuum/vent opening 24 defined therethrough placed in fluidcommunication with vacuum/vent means 26 capable of allowing the fluid ofchoice to flow either in or out of the vacuum/vent opening 24. In apreferred embodiment, the vacuum/vent means would include fluid removalmeans 28 such as a fluid removal pump 30 well known to the artassociated with a control valve 32. The vacuum/vent means 26 would alsoinclude another control valve 34 which when opened would connect thevacuum/vent openings 24 with the atmosphere.

Returning now to FIG. 1 the lower mold surface 16 can also be seen toinclude an upper edge section 36 and a lower recessed section 38 locatedat a lower elevation than the upper edge section, the first fluidlubrication opening 18 being defined through a portion of the upper edgesection, the vacuum/vent opening 24 being defined through a portion ofthe lower recessed section.

The apparatus 10 further includes an upper mold 40 having an upper moldsurface 42, said mold surface having at least one second fluidlubrication opening 44 defined therethrough and placed in fluidcommunication with a second fluid lubrication means 46, in a preferredembodiment comprising a fluid lubrication pump 48 such as an air pumpwell known to the art. The mold surface 42 further includes a fluid ventopening 50 defined upwardly therethrough.

A lower sheet frame 52 having a first opening 54 defined upwardlytherethrough operatively carries or is connected to first clamp means 56located about the upper periphery of the lower sheet frame.

An upper sheet frame 58 having a second opening 60 defined upwardlytherethrough and being operatively connected to or carrying second clampmeans 62 located about the upper periphery thereof is positioned abovethe lower sheet frame 52. The inner periphery of the upper sheet frameis sized to fit in close-spaced relationship adjacent the outerperiphery of the lower sheet frame, the inner periphery of the lowersheet frame being sized to fit in close-spaced relationship adjacent theouter periphery of the lower mold 14.

The apparatus 10 further includes first seal means 64 (FIG. 10) such asan inflatable boot carried by the outer periphery of the lower mold orthe inner periphery of the lower sheet frame and being inflatable toform a fluid-tight seal between the mold 14 and the frame 52. A secondseal means 66 of similar construction to the first seal means 64 isoperatively engaged between the lower sheet frame 52 and the upper sheetframe 58 and inflatable therebetween to provide a fluid-tight sealbetween the frame 52 and the frame 58 when the frames 52, 58 are placedadjacent one another. It should be well recognized that many otherpneumatic and/or mechanical seal systems may be used between the moldand frames 52, 58 to accomplish the same mechanical result.

Apparatus 10 also includes the lower elastomeric sheet 68 formed in apreferred embodiment from natural latex rubber having a thickness of0.060 inch. It should be well recognized in other embodiments that othermaterials having other thicknesses may be used.

The lower elastomeric sheet in a preferred embodiment is clamped aboutthe upper periphery of the lower sheet frame by the first clamp means56, the first clamp means 56 in a preferred embodiment comprising asteel frame attached to the lower sheet frame by screws, incorporating agroove with sealant material therein about the sealing periphery so asto form a fluid seal between the frame clamp means 56 and elastomericsheet 68, as is well known to the art. The lower sheet therefore forms afluid-tight seal across the first opening 54, the lower sheet during aportion of the preformed material shaping process supporting the preformmaterial 12.

Apparatus 10 also includes an upper elastomeric sheet 70 of similarmaterial and construction to the lower elastomeric sheet 68, clampedabout the upper periphery of the upper sheet frame by second clamp means62, the upper sheet forming a fluid-tight seal across the second opening60, the second clamp means 62 mechanically similar to the first clampmeans 56. When sheets 68, 70 are placed adjacent one another to hold thepreform material, a fluid cavity 72 (FIG. 2) is defined therebetween,the fluid cavity placed in fluid communication with fluid removal means74 in a preferred embodiment comprising a vacuum pump 76 capable ofestablishing a vacuum between the sheets.

It should be noted that the useful life of the upper sheet 70 has beenextended to 200-300 cycles during fabrication of the preform shown inFIG. 8 by placing a domestic bedsheet (not shown) between the uppersheet and the upper mold surface. The bedsheet is tied at its fourcorners to the upper sheet frame.

It is well recognized that pumps 30, 22, 76, 48 may be consolidatedwithin a more extensively valved header system, as is well known to theart, so as to reduce the total number of pumps but increase the numberof control valves needed to perform the process sequence.

Apparatus 10 further includes, when the sheets are placed adjacent thelower mold surface, a first fluid chamber 78 defined between the lowermold surface and the lower sheet, the first fluid chamber placed influid communication with the vacuum/vent means and the first fluidlubrication means. A second fluid chamber 80 (FIG. 4) is defined betweenthe upper mold surface and the upper sheet when the upper surface andupper sheet are placed adjacent one another, the second fluid chamberbeing placed in fluid communication with the second fluid lubricationopening 44 and through the fluid lubrication header 82 (FIG. 1) with thesecond fluid lubrication means 46 and the fluid vent opening 50.

It should be noted throughout the specification that, for the sake ofeditorial brevity, when the preform material 12 is held between the twoelastomeric sheets 68, 70, that the entire assembly of material 12 andsheets 68, 70 is referred to as the laminate assembly 84 (FIG. 2).

Apparatus 10 also includes in a preferred embodiment heater means 86(FIG. 1) such as an oven 88 capable of heating the preform material to atemperature sufficient to soften the sizing coating the material andmake the material pliable and susceptible to subsequent forming andcooling to dimensionally stabilize the material in a preferred shape. Inthe preferred embodiment, the preform material consisting of four layersof a combination mat (one side plain roving, one side chopped strandmat) manufactured by Fiberglass Industries Inc., 5 Edison Street,Amsterdam, N.Y. 12010, identified as Fab Matt #2215 is heated from roomtemperature to a temperature of approximately 350 degrees Fahrenheitprior to being placed above the lower elastomeric sheet. It is wellrecognized that other methods besides convection heating within the ovenmay be used to heat the preform material, such as infrared radiation.

In simplest terms it can be seen that the apparatus of the inventionincludes means for holding the preform material in a substantiallyplanar manner so as to prevent wrinkle formation before, during or afterthe shaping process. Furthermore, the means for molding portions of thelaminate assembly to a desired shape can be seen to include the use ofmold means 90, 90A (FIG. 1) which in a preferred embodiment comprise theupper mold 40 and the lower mold 14 respectively, portions of the uppermold surface and the lower mold surface shaped to cooperatively engageabout the laminate assembly 84.

The apparatus can also be seen to include means for placing lubricationin the space that separates the surface of the mold means 90, 90A andthe laminate assembly 84 wherein the lubrication means would includefirst fluid lubrication means 20 and second fluid lubrication means 46as discussed earlier.

The frames carrying the sheets and the molds move relative to oneanother by use of a hydraulically-operated mechanical drive systemoperatively engaged to the sheets and molds as is well known to the art.A working prototype machine has been designed, fabricated, and completedunder the direction of the inventor by Doerfer Inc., 201 WashingtonStreet, Cedar Falls, Iowa, 50613, and has just recently commencedproduction of preformed material for a commercial part.

In operation, the method of the present invention for shaping thepreform material comprises the general steps of holding the preformmaterial between the upper elastomeric sheet and the lower elastomericsheet so as to minimize the wrinkles in the preform material, andthereafter molding the laminate assembly to the preferred shape. Holdingthe preform material between the sheets insures that the material ismaintained parallel to the mold surface as the laminate assembly isformed about the various contours and edges of the mold. As mentionedbefore, the sheets distribute stress concentrations away from "hardedges" formed by drastic contour changes in the mold surface, therebyminimize or eliminate fiber distortions and/or tears or rips in thepreform material.

The sheets being relatively impervious to fluid flow, also allow a fluidlubrication system to be used between the mold surface and the sheets toeliminate binding of the sheets on the mold surface. The sheets maintainthe fibers comprising the fabric under tension as the laminate assemblyis formed to the desired shape. This tensioning mechanism is the primarycontributor to minimizing or eliminating wrinkles in the formed preform.

More specifically, in the preferred embodiment, the preform material isheated to a temperature sufficient to soften the sizing coating thematerial. The preform material is initially placed on the lowerelastomeric sheet and the lower sheet frame 52 is lowered in thedirection indicated by arrows 94 (FIG. 1) downwardly about the outerperiphery of the lower mold. The upper sheet frame 58 is then loweredabout the lower sheet frame. The second seal means 66 (FIG. 2) isactuated and the preform material is thereafter held between the sheetsby actuation of fluid removal means 74 so as to withdraw air frombetween the sheets through evacuation opening 92 (FIG. 2) so as to forma vacuum of approximately 5 inches of mercury between the sheets. Thepreform material stack is now firmly tensioned between the twoelastomeric sheets.

Once a vacuum has been defined and the first seal means 64 actuated, thefirst fluid chamber 78 is effectively defined by the boundaries of thelaminate assembly and the lower mold surface, the first fluid chamberbeing in fluid communication with the first fluid lubrication openings18 and vacuum/vent openings 24.

Portions of the laminate assembly are then formed about the upper edgesection of the lower mold by removing fluid from the first fluid chambersuch as by opening valve 32 and actuating fluid removal means 28. In apreferred embodiment a vacuum in the fluid chamber 78 is established at18 inches mercury. Forming of the preform is initiated becauseatmospheric pressure above the laminate assembly forces it into thelower mold cavity. Complete forming of the preform would occur if themold had simple contours. However, for complex shapes, complete formingof the preform to conform to the lower mold surface 16 is resisted bythe frictional forces between the laminate assembly and the contactpoints of the lower mold surface. Increasing the vacuum level in thefluid chamber 78 does not cause additional conforming because theresistive friction forces increase proportionately to the level ofvacuum applied.

To complete the formation at this point and time, referring now to FIG.3, the upper mold surface is moved downward (in the direction indicatedby arrows 96) into contact with the laminate assembly.

Referring now to FIG. 4, additional portions of the laminate assemblyare formed adjacent the lower mold surface by continued downwardmovement of the upper mold surface. At this point in time the fluidlubrication is initiated to allow the laminate assembly sheets to "freefloat" relative to both mold surfaces. The fluid lubrication process inthe preferred embodiment comprises flooding air adjacent both sides ofthe laminate assembly through fluid lubrication openings 18 and 44. Inthe preferred embodiment the air lubrication flows through 8 holes ineach mold surface, each hole having a 1/8 inch diameter, the holescomprising the first and second fluid lubrication openings. The holesare connected via a regulator to the shop air system and the airpressure feeding the holes is maintained at 25-32 psi.

Prior to start of the fluid lubrication process the vacuum beneath thelaminate assembly is released by, for example, opening valve 34 (FIG.2). The vacuum is seen to be removed from beneath the laminate assemblyby adding fluid to the first fluid chamber. The vacuum is maintainedbetween the two sheets to keep the preform material under tension.

The air that floods the upper surface of the laminate assembly eithervents outwardly past the edge of the upper mold or vents from the secondfluid chamber 80 through the fluid vent opening 50. The air thatlubricates the bottom surface of the laminate assembly enters the firstfluid chamber 78 through lubrication openings 18 and vents throughvacuum/vent openings 24.

Close study of FIG. 4 shows that the laminate assembly is allowed tofloat about the hard edges defined in the mold surface. Note for exampleFIG. 7 wherein the laminate assembly 84 is shown adjacent to but notbinding on the ridge 98 formed in the upper mold surface.

Referring now to FIG. 9, in a representative embodiment of the presentinvention it can be seen that the fluid lubrication openings willtypically be grouped at the portions of the mold surface having thehardest edges or sharpest contours such that air flow is maximized atthe sites of possible binding of the laminate assembly. The fluidlubrication header 100 will typically be located adjacent and willsupply fluid to fluid lubrication openings 102 that have been formed inthe mold surface at the areas of minimum radius.

The vacuum/vent openings 104 have been located in a relatively flatsection of the mold surface at some distance from the fluid lubricationopenings 104, so as to encourage the fluid to flow across a largesurface area prior to venting from the mold beneath the laminateassembly. It should be well understood that many other combinations offluid lubrication and vacuum/vent openings may be used to accomplish thesame mechanical results.

Referring now to FIG. 5 the preform material has now been molded to thecontours of the upper and lower molds. The fluid lubrication process issecured and a vacuum is again reestablished beneath the laminateassembly by removal of fluid through the vacuum/vent openings 24. Theupper mold and the lower mold are now at their closest spacedrelationship.

After the vacuum has been reestablished under the laminate assembly theupper mold 40 is retracted, and after a 30 second delay to allow thepreform material to partially cool the vacuum is removed from betweenthe sheets and the fluid cavity 72 is vented to atmosphere. Simultaneousto the release of the vacuum by venting to atmosphere, the second sealmeans 66 between the sheets is released. After the second seal means 66is released the upper elastomeric sheet is retracted upwardly and thesystem is held in this position for two minutes to allow final coolingof the preformed material.

Referring now to FIG. 6 after the two minute delay the vacuum is removedfrom beneath the lower elastomeric sheet by venting air in throughopenings 24, 18. The first seal means is also deactivated so as to allowthe first fluid chamber 78 to be freely vented to atmosphere. Theelasticity of the lower sheet 68 is used to demold the preform. Thepreform shaping cycle is now complete. The shape preform 104 isthereafter removed manually or by machine and the process repeated for asubsequent preform material shaping process.

Referring now to FIG. 8 a schematic representation of a successfullyfabricated preform that is in the process of being incorporated withinan automotive bumper structure is shown. An initially flat sheet ofpreform material was heated, molded, and the shaped preform 104 wasremoved from between the elastomeric sheets, without any wrinkles. Fiberdistortion at the edges was minimized due to the preform material beingheld parallel to the mold during the forming process and also due to theactuation of the fluid lubrication process as the material was formedabout the mold contour.

It should be well recognized that already partially-shaped preformmaterial may be used at the start of the process, though in a preferredembodiment the preform material is initially flat.

Many other variations and modifications may be made in the apparatus andtechniques hereinbefore described by those having experience in thistechnology, without departing from the concept of the present invention.Accordingly, it should be clearly understood that the apparatus andmethods depicted in the accompanying drawings referred to in theforegoing description are illustrative only and are not intended aslimitations on the scope of the invention.

I claim as my invention:
 1. A method of shaping a fibrous preformmaterial, said method comprising:providing a lower mold having anon-planar surface with a first fluid lubrication opening and avacuum/vent opening, providing an upper mold having a non-planar surfacewith a second fluid lubrication opening and a fluid vent opening, saidupper mold non-planar surface shaped to be cooperatively locatable aspaced distance away from said lower mold non-planar surface, heatingsaid fibrous preform material to a temperature above the softening pointof a sizing coating said preform material, holding in an air-tightmanner the fibrous preform material between an impermeable upperelastomeric sheet and an impermeable lower elastomeric sheet to preventwrinkles in said preform material, the sheets and the fibrous preformmaterial forming an impermeable laminate assembly, a portion of saidlaminate assembly unsupported by said non-planar lower mold surface,defining a first fluid chamber bounded by the lower elastomeric sheet ofsaid impermeable laminate assembly and the lower non-planar lower moldsurface, said first fluid chamber being in fluid communication with saidfirst fluid lubrication opening and said vacuum/vent opening, shapinginitial portions of said lower elastomeric sheet about portions of saidnon-planar lower mold surface by removing fluid from said first fluidchamber, thereby shaping corresponding portions of said fibrous materialheld within said impermeable laminate assembly, defining a second fluidchamber bounded by the upper elastomeric sheet of said laminate assemblyand the non-planar upper mold surface by moving said non-planar uppermold surface downward into contact with portions of said upperelastomeric sheet, said second fluid chamber being in fluidcommunication with said second fluid lubrication opening and said fluidvent opening, shaping additional portions of said elastomeric sheetsabout additional portions of said upper and lower mold surfaces, therebyshaping corresponding portions of said fibrous material held within saidelastomeric sheets, including lubricating outer surfaces of saidimpermeable laminate assembly by adding fluid to said first fluidchamber through said first fluid lubrication opening to provide fluidlubrication between said shaped initial portions and said lower moldsurface and adding fluid to said second fluid chamber through saidsecond fluid lubrication opening to provide fluid lubrication betweensaid portions of said upper elastomeric sheet and said upper moldsurface to prevent said outer surfaces of said impermeable laminateassembly from binding to said upper and lower mold surfaces, and coolingsaid fibrous preform material below the softening temperature of saidsizing.
 2. The method of claim 1 including, prior to the step of coolingsaid preform material, the steps of:removing fluid from said first fluidchamber through said vacuum/vent opening to establish a vacuum in saidchamber, moving the non-planar upper mold surface upward away from saidimpermeable laminate assembly, maintaining a vacuum in said first fluidchamber for a set period of time, and moving the upper elastomeric sheetof said laminate assembly upward away from said shaped preform material.